EPA Facts about Americium-241
What is americium-241? process continues until the stable element bismuth is formed. Americium is a man-made radioactive metal. It is produced in nuclear reactors and during nuclear The radiation from the decay of americium-241 weapons tests when plutonium absorbs and its daughters is in the form of alpha neutrons. particles, beta particles, and gamma rays. Alpha particles can travel only short distances and Americium occurs in several forms called generally will not penetrate the outer layer of isotopes. The most common isotope is human skin. Gamma rays can penetrate the americium-241. body. Beta particles are generally absorbed in the skin and do not pass through the entire What are the uses of americium-241? body. The time required for a radioactive substance to Americium is commonly used in very small lose 50 percent of its radioactivity by decay is amounts in smoke detectors. It is blended with known as the half-life. The half-life of the element beryllium and is used as a neutron americium-241 is about 432 years. source to measure the quantity of water present in soil, as well as moisture and density for How are people exposed to americium- quality control in highway construction. 241? Americium is also used as a source of radiation in medical research and in medical diagnostic Most americium that has been released into the devices. environment has come from atmospheric testing of nuclear weapons. Some americium How does americium-241 change in the has also been released through nuclear weapons environment? production, but this amount is small compared with the amount released during atmospheric Americium-241 is introduced into the testing. environment by the decay of plutonium that is a contaminant from nuclear weapons production Nuclear weapon sites, certain types of nuclear and testing and potentially by certain types of reactors, and industries that manufacture smoke nuclear reactors. Americium-241 is an unstable detectors are potential sources of exposure to isotope. Therefore, as americium decays, it americium-241. Potential pathways of exposure releases radiation and forms “daughter” include ingestion, inhalation, and external elements. The first decay product of americium- exposure from gamma radiation. 241 is neptunium-237, which also decays and forms other daughter elements. The decay
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How does americium-241 get into the liver, and muscle. It generally stays in the body body? for decades and continues to expose the surrounding tissues to radiation. This exposure Americium can enter the body when it is inhaled may eventually increase a person’s chance of or swallowed. When it is inhaled, the amount of developing cancer, but these cancer effects may americium that remains in the lungs depends on not become apparent for several years. the size of the particle and the chemical form of Americium, however, also can pose a risk from the americium compound. Some americium direct external exposure through gamma ray compounds dissolve easily. These compounds emissions. are absorbed through the lungs and enter the blood stream. The forms that dissolve less easily What recommendations has the U.S. are typically swallowed, where some may pass Environmental Protection Agency made into the blood stream, and the remainder will to protect human health? pass through the feces. However, some un- Please note that the information in this section dissolved material that stays in the body goes to is limited to recommendations EPA has made to the bones, where it can remain for decades. protect human health from exposure to Is there a medical test to determine americium-241. General recommendations EPA exposure to americium-241? has made to protect human health at Superfund sites (the 10-4 to 10-6 cancer risk range), which Yes, tests are available that can reliably measure cover all radionuclides including americium-241, the amount of americium in a urine sample, are summarized in the fact sheet “Primer on even at very low levels. These measurements Radionuclides Commonly Found at Superfund can be used to estimate the total amount of Sites.” americium present in the body. There are also tests to measure americium in soft tissues (such EPA has established a Maximum Contaminant as body organs), feces, bones, and breast milk. Level (MCL) of 15 picoCuries per liter (pCi/L) for Whole body testing may also be used to total alpha particle activity, excluding radon and measure americium in the body. These tests are uranium, in drinking water. Americium-241 is not routinely available in a doctor’s office covered under this MCL. because special laboratory equipment is required.
How can americium-241 affect people’s health? For more information about how EPA addresses americium-241 at Superfund sites Contact Stuart Americium poses a significant risk if enough is Walker of EPA: swallowed or inhaled because americium emits (703) 603-8748 or [email protected], or visit EPA’s Superfund Radiation Webpage: alpha particles. Once in the body, americium http://www.epa.gov/superfund/resources/radiation/ tends to concentrate primarily in the skeleton,
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